Polymers which are both amine-functional and carry hydroxyl groups (so-called hydroxy-amino polymers) are increasingly of interest in some fields of application, especially in the field of the polyurethane industry. The reason for this is that the presence of two different types of functional groups, namely the amine functionalities and the hydroxyl groups, enables novel property and processing profiles to be achieved. For example, combining the amino groups, which are significantly more reactive towards isocyanate groups, with the less reactive hydroxyl groups gives rise to the possibility of influencing the progress of curing processes over time in a desirable manner, which has hitherto not been possible or has been possible to only a limited extent in the presence of only one type of the above-mentioned isocyanate-reactive functional groups.
In general, the amino functionality of hydroxy-amino polymers can be introduced into macromolecules by the addition of primary amines or ammonia to low-electron double bonds, for example of the (meth)acrylate type. The addition of amines to (meth)acrylate-group-containing polymers, inter alia to (meth)acrylate-group-containing polyethers, is known per se; for example, such processes are mentioned in U.S. Pat. No. 5,739,192 A1, U.S. Pat. No. 5,597,390 A1, US 2005/0171002 A1, DE 196 16 984 A1, DE 195 08 308 A1, WO 2010/090345 A1, JP 2009/22753 A1 and JP 04089860 A1.
By contrast, the obtainment of the precursor compounds comprising the low-electron double bonds in the prior art is either not described or takes place via condensation reactions that proceed according to the laws of statistics, for example by the esterification of acrylic acid with difunctional polyethers or the reaction of acryloyl chloride with dysfunctional polyethers.
A common feature of all the described processes is that the introduction of double bonds into the precursor compounds of the hydroxy-amino polymers takes place at the expense of the number of hydroxy functions. Accordingly, these processes do not allow the original hydroxy functionality, which in the case of polyether molecules is generally given by the functionality of the starter molecules used to prepare the polyethers, to be retained during the introduction of the amino fractions.
U.S. Pat. No. 4,874,837 A1 discloses a process in which first diethylene glycol or a mixture of diethylene glycol and a low molecular weight polyether polyol having a molecular weight of from 100 to 600 g/mol is reacted with maleic anhydride or a mixture of maleic anhydride and a further anhydride, maleic anhydride and diethylene glycol being used approximately in a stoichiometric molar ratio. The resulting acid group of the semiester is then converted back into a hydroxy group by reaction with an epoxide, before the amino group is finally introduced by Michael addition of diethanolamine, or a mixture of diethanolamine and further amino alcohols containing primary or secondary amino groups, or diamines containing primary or secondary amino groups to the reactive double bond of the hydroxy maleate.
In the case of the process described in U.S. Pat. No. 4,874,837 A1 it is in some cases perceived to be a disadvantage that the process is limited structurally to the use of diethylene glycol or a mixture of diethylene glycol and a low molecular weight polyether polyol as precursor. A possible reason for this is possibly the falling reactivity of the OH groups of the polyether polyol, in relation to the reaction carried out here, as the chain length increases. Moreover, in each case only approximately one hydroxy group of this precursor is reacted with the anhydride. Furthermore, the Michael addition to the reactive double bond is limited to diethanolamine or a mixture of diethanolamine and further amines reactive with isocyanates.
Accordingly, the object of the present invention was to provide a process for the preparation of hydroxy-amino polymers which is more universally usable, it being possible in particular also to produce hydroxy-amino polymers from polyether polyols with a greater chain length. At the same time, the process is to be simple to carry out and is to suppress the formation of secondary products, such, as, for example, transesterification products, as far as possible, so that working up of the process products is generally not necessary.